Wireless telegraph and telephone system



Dec. 24, 1929. D FOREST 1,740,577

wmELEss TELEGRAPH AND TELEPHONE sYswEn Original Filed July 1. 1924 3 Sheets-Sheet l 1N VENTOR Original Filed July 1. 1924 L. DE FOREST WIRELESS TELEGRAPH AND TELEPHONE SYSTEM 3 Sheets-Sheet 2 l l l lll l lwww ii 9} IN f ENTOR Dec. 24, 1929. L. DE FOREST 1,740,577

WIRELESS TELEGRAPH AND TELEPHONE SYSTEM Original Filed July 1, 1924 5 Sheets-Sheet 3 llllwllllwww i2 INVENTOR W QQYS Patented Dec. 24, 1929 UNITED STATES PATENT oF icE LEE DE FOREST, OF NEW -YORK, N. Y., ASSIGNOR T0 DE FOREST RADIO TELEPHONE &

TELEGRAPH COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION 011" DELA- WARE WIRELESS TELEGRAPH AND TELEPHONE SYSTEM Application filed July 1, 1924, Serial This invention relates to wireless telegraph and telephone systems, and contains subjectmatter divided from my co-pending applications Serial Nos. 825,954, filed March 20, 1914:, and 52,176, filed September 23, 1915, which have become patents numbered 1,507,017 and 1,507,016, respectively; This application is a continuation in part of the first mentioned application.

The object of the invention is to provide a wireless communication system as well as novel circuit arrangements employed in con nection therewith, whereby, in connection with the three-electrode vacuum tube, regeneration or re-amplification takes'place, which, in addition to securing a more sensitive receiver also constitutes an exceedingly eflicient transmitter, and the same equipment may be used for both transmission and reception.

Further objects will appear more fully hereinafter.

The invention consists substantially in the construction, combination, location and relative arrangement of parts, as well as the circuit arrangements employed in connection therewith, all as will be -more fully hereinafter set forth, as shown in the accompanying drawings, and finally pointed out in the appended claims.

Referring to the drawings Fig. l is a circuit diagram showing one arrangement embodying my invention wherein the system serves as a generator of continuous oscillations.

Fig. 2 is a circuit diagram showing an arrangement whereby the receiver is not effected by the energy being radiated from the home antenna.

Fig. 3 is a circuit diagram showing an arrangement wherein the same device serves as an oscillation detector and generator.

Fig. 4 is a similar view, showing a modified arrangement wherein a detector separate from the oscillation generator is employed.

Fig. 5 shows a modified circuit arrangement employed in connection with the ther- No. 723,488.- Renewed May 11, 1929.

continuous oscillations, the use illustrated being that of a receiving circuit.

The same part is designated by the same reference character wherever it occurs throughoutthe several views.

In the drawing N designates the antenna for transmitting and receiving. Adjustably connected in the antenna circuit is an inductance S. The antenna circuit is connected to earth or other capacity E, and where the apparatus is to be used for telephonic communi cation, the antenna has associated therewith or includes a microphone transmitter M. /Vhere the apparatus is to be used for telegraphing, a Morse telegraph key, not shown, is bridged across a portion of the inductance S. The inductance S is in the form of a coil with which is inductively associated, preferably in loose coupled relation, an inductance coil P, one terminal of which is connected to auxiliary or cold grid electrodes G, G, arranged within an evacuated bulb or vessel U. The other terminal of coil P is connected to the cold plates or electrodes W also arranged within the bulb U. Connected across the terminals of coil P is a variable capacity C In series with the coil P and electrodes G, I place a blocking condenser G and if desired (see Fig. 3) in series with the coil P and electrode plates W, I place an inductance coil L, across the terminals of which is connected 2. variable capacity C Contained in the bulb U is a hotelectrode F, which is, in the form shown, a

filament or glower, to which current is supcycles per second, or higher. For wireless telegraph work the frequency of the generator may be very much lower, for example, five hundred per second.

A telephone receiver T is connected on one side in series with the plate electrodes W, and on the other side in series with the filament F. In circuit with the telephone T, is a source of current supply indicated at B, as a battery, the purpose of which is to impress an electromotive-force between the cold plate electrodes W and the filament F.

By reason of the arrangement above described, the device U with its associated electrodes and filaments and their associated circuits and connections, becomes a generator of alternating or pulsating electric currents or continuous oscillations of high frequency in the circuit of coil P, the frequency of which depends upon the spatial relation of the electrode members contained therein, the value of the electromotive-force impressed across the electrodes, and the amount of inductance and capacity included in or associated with the circuit of said coil. In the arrangement shown in Fig. 3 the frequency of such oscilla tions may be varied by varying the capacity of condensers C or C.

By the reason of the relation of coils P and S, the oscillations in the circuit of coil P are impressed upon the antenna-earth system and with a natural period of oscillation in the antenna-earth system the same as that of the oscillations in the circuit of primary coil 1.

The amplitude of the oscillations induced in the antenna-earth systemas above described may be varied by and in accordance with sound waves falling upon the microhone transmitter M, int-he usual manner.

imilarly, a telegraph key associated in the antenna-earth system may serve to control the emission of wave trains in accordance with the telegraphic code, or, if desired, and

' as shown, if the key K is associated with the antenna-earth system in such a manner as to short-circuit a portion of the inductance S, the wave length of the emitted wave trains may be altered in a manner well understood in the art...

It will be seen that, in the arrangement shown in Fig. 3, the device U with its associated electrodes and filament and circuit arrangement therefore combines within itself the functions of a source of continuous oscillations and also those of a detector, like the audion detector, and its detector functions are in no way impaired by its simultaneous operation as an oscillation generator. Incoming electromagnetic signals influence the circuits of the electrodes G and W, and produce an alteraticn in the conducting qualities of the medium between the plate and grid electrodes and consequently any received si nals when attuned to the proper wave Ian %2 will be heard in the receiver T, during the.

pauses between the signals being made by the operation of the key, or between the words spoken into the microphone transmitter M; By this simple arrangement, as described, I

am enabled to secure duplex operation whether for telegraphing or telephoning, employing the same apparatus for transmitting and receiving.

It is obvious that provision may be made to protect the telephone receiver T in case large amounts of current are to pass across the space in the bulb U. Any suitable means may be employed for this purpose, as, for instance, the usual high resistance telephone receiver may be employed which, if desired, may be coupled to the circuit containing the battery B, electrodes W and filament F, in any suitable or well known manner.

In Fig. 4 I have shown an arrangement wherein a detector device independent of and separate from the oscillation generator is employed' In this arrangement I employ for the detector an evacuated bulb U with a filament F and a grid G and a plate W similar to corresponding parts above described with reference to bulb U, the filament circuit being supplied with current from a current source A controlled by a rheostat R the plate W constituting one terminal of a circuit which contains. the telephone receiver T and current source B the other terminal of said circuit being connected to one side of the filament circuit. One terminal of another circuit is connected to the grid G the other terminal of said circuit being connected to the other side of the filament F This last mentioned circuit is inductively associated with the oscillating circuit which contains the coil P, as, for instance, through the coils L L the latter being shunted by a variable capacity C By means of the variable condenser C this secondary system can be accurately attuned to the frequency of the received oscillations. It is ob vious that this secondary receiver circuit may be associated with the antenna earth system, or with the circuit of coil P, in any other suitable or well known manner.

Any suitable means may be employed to supply the necessary inertia to the circuit of battery B, such, for instance, as by including an impedance coil I, in said circuit.

Fi 2 shows a balanced antenna circuit associated with the. source of-the oscillations S and its inductances and capacity so proportioned relative to the capacity of the an tenna itself that the total eflect of the oscillations from the source-S upon the receiver transformer BL is neutralized while at'the same time impulses received on the antenna N, preferably of a slightly different frequency from that of the oscillations from S", are clearly received in the properly attuned receiving circuit L L and transmitted to the audion detector U andtranslated there into telephone currents in the circuit T B in th well known manner.

In Fig. 5 I show a modified' arrangement wherein the reamplification, and if desired is produced by a differentspecie of circuit,

i. e., a circuit where the output or. plate filament circuit is inductively coupled with the input or grid filament circuit. Inthis arrangement the coupling is by means of an audlo frequency transformer whose coil L located in the grid filament circuit is induc-. tively coupled with its related coil U, which is included in the plate filament circuit. Each of these coils is preferably shunted by a variable condenser C and C respectively. The grid filament circuit also includes transformer coil P shunted by a variable condenser C and the plate filament circuit includes the telephone receiver T and the B battery B. The coil P is inductively associated with the inductance L which is in the antenna earth connection. Where it is vdesired to generate high frequency currents it will be understood that-high frequency coils L and L will be employed with or without the iron core I in accordance with the type of high frequency transformer used.

I am unable at the present time to give a complete explanation of the theory of action of the apparatus when operating as a gen erator. I have discovered, however, as hereinabove stated, that a system constructed as shown and described and energized from a suitable current source, becomes the seat of continuous high frequency oscillations. Undoubtedly the phenomena involved depends upon the effect of successively applied charges or surges of potential upon the grid and plate elements and 'havin the power to effect momentarily the con activity of the medium between the filament and plate electrodes in such manner thatthe current variations in the grid filament circuit produce corresponding variations in the plate filament circuit which are fed back to the grid filament circuit to add their effects to the initial variations, which latter, thus reinforced, create and form greater variations in the plate filament circuit which are, in turn, fed back to .the grid filament circuit to still further amplify the variations inthat circuit, and

so on. The energy of the variations of each circuit reacts upon and increases that of the other circuit until a maximum sustained alternating current is finally produced, Whose frequency can be controlled by varying the electrical constants of the associated circuits. In other words, the amplifying action incident to the feeding back of energy from the one circuit to the other increases until oscillations are produced which, once set up, are self-perpetuating, analogous to the whistlingor surging action observedwhen a telephone receiver and microphone transmitter, connected together in the same or coupled circuits, are so placed as to react one on the other mechanically and electrically.

Having now set forth the objects and nature of my invention, what I claim as new and useful, of my own invention, and desire to secure by Letters, Patent, is

1. In a radio signaling system means for generating oscillations comprising an inductance, a discharge device having an anode, a cathode, and an impedance-varying element, a lead from said cathode to a point in said inductance, a lead from said anode to said inductance, a lead from said impedance-varying element to said inductance, and an electric capacity in effective shunt to at least a portion of said inductance, including at least a portion of that part of said inductance which lies between the leads from said cathode and said impedance-varying element.

2. In a radio signaling system means for generating oscillations and transmitting them to a work circuit, comprising an inductance, a discharge device having an anode, a cathode, and an impedance-varying element, a lead from said cathode to a point in said inductance, a lead from said anode to said inductance, a lead from said impedance-varying element to said inductance, and an electric capacity in effective shunt to at least a portion of said inductance including at least a portion of that part of said inductance which lies between the leads from said cathode and said impedance-varying element.

3. A transmission circuit, a discharge device having a connection with said circuit, means for varying the discharge of said device in accordance with sounds, said connection serving to transmit signaling waves from said device to said circuit and from said circuit to said device, and a receiver for said waves associated with said device.

4. A two-way signaling set comprising a source of signaling energy, a circuit for transmitting and receiving signaling energy, a dis charge device for transmitting energy from said source to said circuit, a transmitter for controlling the discharge device and a signal receiver in the circuit of said discharge device.

5. In a signal transmission system, a twoway signaling set for such system having transmitting and receiving circuits including a local receiver, said transmitting circuit including a source of signaling waves, means for controlling said source, a discharge device for transmitting said waves and for rendering them receivable in said local receiver, and send receiving circuit including elements of said discharge device for rendering the incoming waves receivable by said local receiver.

In testimony whereof I have hereunto set my hand on this 23rd day of J une-A. D., 1924.

LEE DE FOREST. 

